What is Stiction? 


Stiction is the resistance to the start of motion usually measured as the difference between the external force being applied in order to overcome the static friction and the force to maintain movement between the two contacting or working surfaces.

It can result from: corrosion, cold welding, breakdown of lubrication, build-up of deposits, chemical reactions, breakdown of the sealing components…

Many studies and organizations have defined stiction, in different ways.  Yet, all agree that stiction is the act of being “stuck” by static friction which prevents one surface from moving against another.  Further, if the external force becomes greater than the static friction, the stiction between two surfaces will be overcome and the object will begin to move again.

Stiction research shows other failure modes become significant when these products do not move frequently – some failure modes become significant if a product is static (motionless) for 100 hours. When O-rings and other seals are part of a product, many failure modes become significant when the product remains static for a week or more, for most of these failures are dangerous.  Improvements in safety and reliability can be obtained with stroke testing or even partial valve stroke testing, for once the stiction is broken via movement the friction build begins over. 

Related Items

Back to Basics 01 - Functional Safety

Back to Basics 02 - Safety Integrity Level (SIL)

Back to Basics 03 - Safety Instrumented Function (SIF)

Back to Basics 04 - Safety Instrumented System (SIS)

Back to Basics 05 - What is a Safety Function?

Back to Basics 06 – IEC 61508

Back to Basics 07– Safety Lifecycle – IEC 61508

Back to Basics 08 – IEC 61511

Back to Basics 09 – Safety Lifecycle – IEC 61511

Back to Basics 10 – How Does a Product Get a SIL?

Back to Basics 11 – How is SIL Used by an End User?

Back to Basics 12 – What is IEC 61508 Certification?

Back to Basics 13 - How Do I Start IEC 61508 Certification?

Back to Basics 14 - Systematic Capability

Back to Basics 15 - Architectural Constraints

Back to Basics 16 - PFDavg

Back to Basics 17 - PFH (Probability of dangerous Failure per Hour)

Back to Basics 18 – Route 1H

Back to Basics 19 – Route 2H

Back to Basics 20 – Safe Failure Fraction, SFF

Back to Basics 21 – The B10 Method

Back to Basics 22 – Cycle Testing

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